The Papa Becomes the Baby
by TeddyBearTy
Summary: When Papyrus and Sans see that their father is working consistently without rest, they decide to treat as a baby. Gaster does not enjoy it. But he will...soon. WARNING: ABDL THEMES AND AGEPLAY! (Gift for diaperhorse on DeviantART) (ON HOLD)
1. The Start

**Yay for ABDL!**

 **Anyways, it's been a while since I typed an Undertale ABDL fic! As such, I wanted to make this one especially for a dear friend of mine.**

 **Her name is diaperhorse, a good pal of mine on DeviantART. She also enjoys ABDL and wanted me to make a fic of Gaster being babied by his sons. And she got her wish.**

 **I hope all of you enjoy it and I take no ownership to any of the characters!**

Gaster opened his eyes and realized that he wasn't in his bed.

His pupils scanned the room and the first thing he saw was a mobile slowly twirling above his head. The little plush lambs that were dangling on it smiled down at him as he awoke.

"What...?" he sat up and looked around. "This isn't my room."

He looked all over the place to realize that this very room _was_ his. However, there were a few differences from how it looked originally. Like all of his novels and science books that he had were replaced with stories for children. And all the new furniture like the changing table that stood perpendicular to the left side of the bed, and the rocking chair to the right.

And the crib he was sleeping in.

"Sans!" he called his sons. They may know what's going on. "Papyrus!"

No response.

He grabbed the crib bars and realized just as short they were. The crib was slight larger than a crib but the length of the bed actually came from the width of it, not the height. And because of this, he decided to climb out.

It was difficult to say the least.

For starters, his legs were as shaky as gelatin. When he lifted one of his legs, the one that was supporting his weight started to shake. He solved this by grasping tightly onto the railing of the crib and lifted himself up. But it was so hard to do this. It felt as if he was lifted two hundred pounds of weight without magic.

Magic...

He plopped back down in the crib and concentrated. Usually, it would come naturally. He would've lifted into the air in a purple aura and walk out of the room easily in order to see what was happening.

But...he just couldn't get off the ground.

"What the...?" he tried concentrating harder.

He squeezed his eyes shut and clenched his fists, doing his hardest to get off the mattress and leave the room. Nothing happened.

"Why is nothing happened?!"

"hey, i see you're awake! morning!"

Gaster turned his head to see the shortest of his sons peek out of the doorway. He opened the door wider and walked inside. He put his hands in the pockets of his hoodie as he asked.

"did ya sleep well?"

"Sans!" his father grabbed the railing of the crib and lifted himself up, cringing as he struggled. Once he was able to stand up, he asked. "What's going on?"

The smaller skeleton's grin grew a little as he stated. "hey, ya know, it's not nice to not answer someone's question dad. but..." he shrugged. "since ya seem concern about your situation, i'll explain. me and paps saw you stressed out a couple weeks back about your project in the lab. how you weren't getting it to work after working on it for like three weeks straight. we gave you a few muscle and magic relaxants and made this in order to get you to...well relax. so..." he smirked. "are you enjoying yourself?"

"No!" he answered. "Why would you two think _any_ of this was a good idea?!"

"ya still seem stressed..." the short skeleton muttered, looking away from his father as he rubbed his chin. He then snapped his fingers, turning back to the older skeleton. "maybe some breakfast will make you relax a bit more!"

Suddenly, his hand started to glow a bright blue as Gaster's body was covered in the same aura. The older skeleton yelled and screamed as he was being lifted off of the ground, begging for his son to let him go. He didn't oblige.

They eventually walked into the kitchen, where Papyrus was busy making spaghetti, the usual dish. Sans smiled as he placed his hands behind his back, still keeping his dad in the air

"hey pap! someone's up and he's kinda fussy~!"

"I CAN HEAR HIM SANS." the taller brother stated as he stopped his cooking and turned his head to see Gaster floating in midair. He glared down at his brother. "SANS..."

"yeah...?"

"PUT HIM DOWN."

Sans obliged, gently placed their dad on the floor. As he was placed down, Gaster felt that they was something soft on his bottom. He looked down at himself and noticed that he was wearing a purple T-shirt and a large white diaper. His frown deepened.

"WHAT'S WRONG FATHER?" Papyrus asked. "NOT FEELING TOO GOOD?"

"Pretty much." Gaster replied. "Especially the fact that you two SHOVED ME IN A DIAPER AND MADE MY ROOM LOOK LIKE A NURSERY!"

"OH~!" Papyrus smiled. "YOU SAW YOUR ROOM! DID YOU LIKE IT?"

"NO!"

The younger brother turned to the eldest. "WOWIE...HE REALLY IS FUSSY!"

"told ya." Sans stated. "now if you excuse me, i'm gonna go watch tv."

"MAKE SURE YOU FEED ROCKY WHILE YOU'RE OUT THERE!"

"ok."

Papyrus sighed as he muttered. "HE'S NOT GONNA DO IT..." he then straightened up and smiled towards his father, who was currently struggling to get off the cold kitchen floor. "ANYWAYS," he picked up his dad bridal style before he could hurt himself. "ARE YOU READY FOR BREAKFAST?"

Gaster huffed but nodded just as his stomach growled. He needed some food in his system.

"TO THE TABLE! NYEH HEH HEH!" the younger skeleton piped as he walked towards the living room, his dad looking around to see any other changes were made to their home.

 **This story will possibly be five to ten chapters long (hopefully) so I hope you all stuck around for more!**


	2. Up and Hurting All Over

**A little bit of a filler chapter. I've been having a little bit of a writer's block.**

 **Anyways, I hope you like it!**

 **I own none of the characters.**

Gaster was not happy.

Sure, breakfast was okay. A little mushy but it was pretty tasty. He would've felt better if he was sitting in a normal chair like his sons. He also would have liked if Papyrus wasn't feeding him like a baby with the little 'here comes the airplane' technique.

He didn't know why that methods worked for actual babies but it wasn't doing it for him. However, after a while of him rejecting the childish treatment, he saw that his younger son was practically begging him to eat while the eldest glared from a distance.

The scientist immediately felt a chill go up his spine at that look. Due to this, he started to consume his breakfast without hesitation.

After all the food was eaten, Papyrus placed his father in a large playpen that sat towards the left side of the couch, near the dining room area. He then placed a purple pacifier in Gaster's mouth as he told his brother to turn on something educational while he went to clean the dishes.

The smallest of the siblings complied and turned on some little kid show that the doctor was unfamiliar with.

He sighed, glaring at the large purple dinosaur sing and dance on the screen before turning to his eldest son. He spat out his pacifier before asked. "What is this?"

"the tv show?" Sans smiled. "it's barney and friends. alphys told me that kids on the surface love this show! although, it doesn't explain why the dvd got down here in the first place." he lightly shrugged before closing his eyes.

Gaster nodded before turning back to the television. "Why would anybody find this amusing?"

Sans shrugged once more, this time it was more sluggish.

His father started to lift himself up, holding onto the railing of the pen as he did it. He then started to look around, staring back at the other skeleton in the room with him to make sure he did react.

The sound that reached the scientist was soft snores.

Sans was fast asleep.

"Why am I not surprised…?" Gaster muttered before jumping a little and pushing himself up.

Like his crib, the large built of the pen came from the width of it not the height. Usually, he would be able to walk over it not trouble but now, his legs were not cooperating.

Eventually after a bit of struggling and grunting, he was able to lift his body over the railing. He smiled a little at a job well done until he realized.

How in the world was he gonna get down?

It wasn't that big of a drop but he knew it would still be difficult. He would end up landing on his face or his stomach if he just dropped to the floor. And him landing on his feet was out of the question.

Before the scientist could think of a strategy to get out of his predicament, a certain voice broke the silence.

"OH MY ASGORE!"

Sans immediately jumped up by the shout and Gaster fell onto the floor with a loud thud.

Gaster ended up landing on his face, just the spot he wanted to avoid, and clenched his teeth together as he rubbed the spot. The impact really hurt and he was doing his best not to cry.

He was failing miserably.

"SANS!" Papyrus barked as his sibling turned to him. "HOW COULD YOU BE SO IRRESPONSIBLE?!"

"television puts me to sleep." Sans replied. "we've been over this."

"I GAVE YOU SPECIFIC INSTRUCTIONS TO WATCH HIM!"

"sorry bro…"

"NOW FATHER…" he bended down and lifted up the skeleton he was referring to and saw that he was sobbing. It was quiet but it was there. Papyrus sighed. "WHAT YOU DID WAS VERY BAD. WHAT DO YOU HAVE TO SAY TO YOURSELF?"

"My face hurts…" he sniffled, wiping away the lavender tears that slipped from his sockets.

The youngest skeleton let another sigh slip from his teeth before nuzzling his dad's head. He got back up and walked him upstairs. "I'M GOING TO CHECK TO SEE IF FATHER HAS ANY INJURIES. SANS, GO DO SOMETHING PRODUCTIVE LIKE PICKING UP YOUR SOCK."

"ok."

"I MEAN IT."

"ok."

"NOW."

"ok."

Papyrus then walked up the stairs, leaving his brother alone. Sans walked over to the sock that laid near the steps with several notes attached to it. He grabbed the sock and placed it on his foot but not before he slipped one of the socks he was already wearing in its place.

He smirked and sat back down on the couch.

"my work here is done."

 **Any suggestions? Leave them in a review!**


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